Feb 22, '06 06:02:00AM • Contributed by: kurnelpanik
Curious about how to booting your Intel iMac from either a USB2.0 iPod or an external Firewire drive? It is possible, and here's how. This has been tested with a 5G 30GB USB2.0 iPod with Video and an external FW400 60GB hard disk enclosure.
The key issue is the disk partioning scheme that Intel Macs expect to see. GPT (or GUID), remember? Well it appears that the EFI in an Intel iMac also supports booting from Apple Partition Map (APM) partitioned disks as well. The Intel iMac's Install DVD Disk One, for instance, uses an APM and NOT a GPT scheme.
So how to fool the system and it's hardware? Credit due to Joel and the TidBits article (referenced in this earlier hint) for setting the germ of the idea in my mind.
Take a current 5G iPod USB2.0 and restore it as though new, using the iPod Updater with the iPod connected to an Intel iMac (this part probably isn't necessary). Interestingly, while the iPod updater itself is a Universal Binary, the Restore function creates an APM partitioning scheme on the iPod when you restore it.
So how to get Mac OS X 10.4.4 (Intel) onto the iPod? I still wanted to use the iPod for Music and Video, so erasing and partitioning were not allowed; it had to be single volume. And you can't select this volume as the installation destination while booted from Install DVD, because the installer doesn't like its partition map.
ASR (Apple Software Restore) to the rescue (and the following was done on a live system):
- With iPod connected and mounted on the Desktop, open Terminal.
- At the prompt type the following:
Replace imac_boot with the name of your iMac's boot disk, and ipod_name with the name of your iPod as seen on the Desktop. If you are unsure, do an ls /Volumes first to see the proper names. Then press return once and authenticate.sudo asr -source /Volumes/imac_boot -target /Volumes/ipod_name
This will clone the internal boot disk system to the iPod. How long will it take? My boot disk had roughly 8.5GB of data. Cloning that with ASR took around 25 minutes. - When the clone completes, you will probably get a message in Terminal about the System on the iPod not being blessed. I did, but the fix is easy. Just type the following, then press Return and authenticate when asked:
sudo bless -folder /Volumes/ipod_name/System/Library/CoreServices - Now go to the Startup Disk System Preferences pane, and verify that you can see the iPod listed as a valid boot disk. Select it and gently click Restart. Startup is slower than booting through Firewire from a 3G iPod on PPC Mac, but it works.
I use an external FireWire drive for system troubleshooting, and it was already partitioned and had a current version of 10.4.4 for PPC on one partition, with applicationss and backups only on the other chunk. Just follow the same steps as above, and you will get the same result.
The beauty of this solution is that you now have an external FireWire disk that will boot either current PPC hardware or current Intel iMac hardware from different partitions on the same physical disk, using an Apple Partition Map partitioning scheme. Simply select the appropriate partition when doing an option key (Startup Manager) boot. In fact, you should only see one of the two partitions anyway, as one of the two available systems will not work with the connected hardware.
Run Repair Permissions from within Disk Utility after testing. I didn't find anything amiss, though there seem to be awful lot of the "we are using special permissions" type messages. These appear everytime you run Repair Permissions, and are not related to the cloning job you've just performed. A check of the system.log file post-boot off the iPod also showed nothing out of the ordinary either.
Caveats? No warranties, guarantees expressed or implied. There may be, as yet, uncovered issues. Proceed at your own risk as always.
